Pressure gain combustion heat generator

ABSTRACT

Disclosed herein is an efficient heat generation device where fuel is burnt in a pressure gain combustion process. The heat generating system has an inner combustion chamber that is housed in heat exchangers. The combustion chamber walls, in one form, include fluid conduits. While different fluids could be utilized, water is most common and the term water herein is intended to define water and all functional equivalents. The water conduits (tubes) may be multi-pass longitudinal, parallel to the combustor axis or they may be winded around the combustion chamber in a spiral fashion. The combustion products exiting the combustion chamber enter the outer liner where water tube bundles extract the heat of the combustion. One embodiment also utilizes an air preheating stage. Heated water and steam generated in the heat exchanger stages wrapped around the combustor enters the final heating stage where it passes through the flame accelerators in the combustion chamber. The flame accelerators within the combustion chamber are in the hottest region in the combustor and therefore exchanging heat at high temperatures increases the efficiency of the steam generation cycle. It also increases the produced steam quality.

RELATED APPLICATIONS

This application claims priority benefit of U.S. Provisional Application 61/245,963, filed Sep. 25, 2009 and incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE a) Field of the Invention

The invention is in the field of heat generation; more specifically it deals with heat generation using pressure gain combustion, such as for example the pulse detonation system which is described in U.S. patent application Ser. No. 12/560,674, filed Sep. 16, 2009 and incorporated herein by reference.

Pressure gain combustion utilizing detonation based combustion is a high speed combustion process where the reaction zone is coupled to a shock wave traveling at supersonic speeds. The result is a higher pressure gain compared with subsonic or near constant pressure combustion. Detonation based combustion is thermodynamically more efficient because it approximates a near constant volume (pressure gain) condition to produce higher pressure and temperatures.

One method of initiating detonation waves in the combustor is to accelerate the flame through turbulence using obstacles along the flow path. A turbulence-enhancing device known as Schelkin spirals installed along the entire length of the combustion tube is such a device. The spirals increase deflagrative flame speeds through increased turbulence and flame mixing and produce ‘hot-spots’ that in turn result in micro-explosions which then coalesce to form a stable detonation front.

Presented here is the use of detonation based pressure gain combustion utilizing Schelkin spirals which are constructed from hollow tubes. The tubes forming the Schelkin spirals also contain fluid which is heated by the combustion process to increase boiler efficiency.

SUMMARY OF THE DISCLOSURE

An efficient heat generation device is introduced where fuel is burnt in a pressure gain combustion process. The heat generating system has an inner combustion chamber that is housed in heat exchangers. The combustion chamber walls are covered with fluid conduits. While different fluids could be utilized, water is most common and the term water herein is intended to define water and all functional equivalents. The water conduits (tubes) may be multi-pass longitudinal, parallel to the combustor axis or they may be winded around the combustion chamber in a spiral fashion. The combustion products exiting the combustion chamber enter the outer liner where water tube bundles extract the heat of the combustion. There is also an air preheating stage further downstream. Heated water and steam generated in the heat exchanger stages wrapped around the combustor enters the final heating stage where it passes through the flame accelerators in the combustion chamber. The flame accelerators are in the hottest region in the combustor and therefore exchanging heat at high temperatures increases the efficiency of the steam generation cycle. It also increases the produced steam quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a highly schematic view of a sample embodiment of the pressure gain combustion steam generator;

FIG. 2 is a highly schematic view of a second sample embodiment of the Pulse detonation steam generator; and

FIG. 3 is a highly schematic view of a third sample embodiment of the pulse detonation steam generator.

DETAILED DESCRIPTION

The detonation based Pressure Gain Heat Generator (PGHG) is composed of an inner combustion chamber, where the air-fuel mixing and combustion takes place. The combustion chamber is composed of an inlet section where air is introduced through radial inlets and a fuel inlet injecting the fuel axially towards the air jet. The mixed air-fuel travel down the combustion chamber and, in one form, passes through a divergent nozzle and a porous plate for stratification. At a specific time, when the air-fuel mixture has filled the required volume of the combustor an ignition system is triggered and the air and fuel mixture is ignited. The flame front propagates in the combustion chamber and accelerates by the turbulence generated in the combustor.

One feature used in pressure gain combustors is a spiral shaped obstruction in the combustion chamber that generates turbulence and increases the flame velocity. This feature is generally called a flame accelerator, and in one form these flame accelerators are in a particular arrangement called a Schelkin spiral. The flame accelerators are located in the combustion chamber and are typically the hottest region in the combustor. Therefore, heat extraction in the accelerators will be at high temperatures and therefore highly efficient. The idea in this disclosure is to build the flame accelerators as hollow tubes, where the operating fluid is passed through the spiral for heat extraction. The heat transfer at the flame accelerators will be at high temperature and therefore in the final stages of heating the fluid. This heat is a portion of the heat generated by the detonation process. Therefore, the outlet of the PDC is passed through a set of heat exchangers that extract further heat from the combustion products. The heat exchangers utilized for this purpose may have various designs such as tubular, shell and tube or plate heat exchangers. Sample embodiments are explained here. In the first concept 20, FIG. 1, the combustion chamber 22 is covered in a concentric tubular heat exchanger 24 design; the inner tube being the combustion chamber 22 with the detonation section and flame accelerators 26 such as for example Schelkin spirals. The outer section is a three way heat exchanger. In this chamber, combustion air entering inlet 28 is entered in a counter-current direction and is heated by the heat transferred through the walls of the combustion chamber 22. Also, water pipes 30 are situated in this chamber that heat the feed water 32 and generate steam which exits through a heated fluid (steam) discharge 34. Therefore, in this tubular heat exchanger the heat transferred through the combustion walls is transferred to the water in the tubes and also preheats the combustion air.

Air (exhaust 36) exited from the combustion chamber 22 is then rerouted 180 degrees and passes through another liner 38 that houses the aforementioned tubular heat exchanger 24 and functions as a muffler. Therefore, further heat is transferred to the tubular air preheater-water heater section through the outer walls of the tubular heat exchanger 24. The outer liner is equipped with baffles and water tubes to extract heat from the combustion products. This section operates as a recuperator for the steam generation process. At the discharge 40 of the outer liner 38, the combustion products are exhausted.

The overall design of the steam generator explained above is a counter-current flow. The circuit of different streams is explained here: water 32 enters the system at the recuperator heat exchanger. Water is passed through tubes and preheated by the combustion products. Preheated water enters the water tubes located in the tubular heat exchanger and heats up further. At the final stage, water (or steam) is passed through the flame accelerators 26 which are the highest temperature component in the system and extract further heat at high temperature. The outlet of the flame accelerators 26 (saturated or superheated steam) is the output 34 of the steam generation device.

Air 28 enters the system at the air pre-heater tubular heat exchanger and once heated, it is passed to the mixing chamber where the air is mixed with fuel 41 and then the combustion chamber 22 where it is detonated. In one form, a ignition source 44, such as a spark plug or laser is utilized to initiate detonation. The detonated mixture travels through the detonation section and is partially cooled by the heat dissipated to the flame accelerators 26 and combustor walls 22. After this stage air passes through the heat exchanger 24 in the outer liner 38 and heats the water in the tubes 30 and then exhausted 36.

Another design that can utilize the high efficiency detonation heat energy is depicted in FIG. 2. In this embodiment, similar elements to those shown in FIG. 1 are designated with a numeral 1 prefix. In this design, the inner combustion chamber 122 is similar to the combustion chamber 22 in the first embodiment explained above. The mixing chamber where air 128 and fuel 142 are injected and mixed, the ignition and detonation chamber are as explained in the first embodiment. The preferred orientation in this design is vertical such that the detonation wave travels through the combustion chamber in vertical direction, upwards. The walls of this combustion chamber 122 are covered with water pipes 130 extending along the combustion chamber, parallel to the combustion chamber axis. The water pipes may be single pass or multiple U-passes. Heat generated in the combustion chamber is transferred through the combustion chamber walls and the tube walls to feed water 132 and heats the feed water. Heated water or steam generated in the pipes is then passed through the flame accelerators 126 such as for example Schelkin spirals to gain further energy. The outlets of the flame accelerators is saturated or superheat steam 134 and is discharged from the steam generator.

Combustion products exiting the combustion chamber 122 are then passed through the outer liner 138, in one form comprising a recuperator for further heat extraction. An air preheater 150 is also utilized to heat the combustion air 154 by the flue gas 152 before it's exhausted.

The path of water/steam through the steam generator is as follows: water 132 enters the pipes in the outer liner 130 (recuperator) where it's heated by the combustion products. Water is heated as it flows in the pipes towards the center of the heat generator where pipes are attached to the outer walls of the combustion chamber 122, where it is further heated and then passes through the flame accelerators 126 for final stage heating. The heated fluid 134 exiting the flame accelerators is discharged from the steam generator 120 and may be used for steam applications.

A third embodiment is depicted in FIG. 3. In this concept, the combustion chamber is covered by a water/steam drum 260. In this embodiment, similar elements to those shown in FIGS. 1/2 are designated with a numeral 2 prefix. The drum diameter and mechanical design is selected such that it can tolerate high pressure steam. Water boils in the water drum and steam rises in the drum resulting in a steam volume 258 up in the drum and boiling water 256 in the bottom portion. The steam generated in the drum is passed through the super-heater flame accelerators 226 for further heating and then discharged 234 from the steam generator 220. In this design, the walls of the combustion chamber 222 are in continuous conductive contact with a chamber of water 256 resulting in more efficient and direct heat transfer from the combustion chamber 222 to the operating fluid 256.

Similar to the previous embodiments, feed water 232 enters the heat exchanger 230 passes of the recuperator 238 and preheats before entering the water drum 260. Water from the recuperator enters the water drum 260 from the bottom and get further heated by the combustor 222 walls. The rise in temperature pushes the heated water upwards due to buoyancy. Once water 256 starts boiling, steam bubble start rising to the water surface and join the steam volume 258 on the top of the drum 260. The saturated steam generated on top of the drum will go through the flame accelerators 226 and then discharge 234 from the system.

If saturated steam is required in the outlet, the flame accelerators may be linked to the water 256 in the drum 260 rather than the steam section 258. In this design, the heat transferred to the flame accelerators will be transferred to water and saturated steam is produced.

While the present invention is illustrated by description of several embodiments and while the illustrative embodiments are described in detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the scope of the appended claims will readily appear to those sufficed in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants' general concept. 

1. A pressure gain combustion heat generator comprising: a. an air/fuel inlet; b. a pressure gain combustion chamber in fluid communication with the air/fuel inlet; c. a feed fluid inlet; d. at least one flame accelerator within the combustion chamber wherein the flame accelerator comprises a fluid conduit therein; e. wherein the fluid conduit with the flame accelerator is operably configured to facilitate heat transfer to a fluid therein; and f. a heated fluid outlet.
 2. The pressure gain combustion heat generator as recited in claim 1 further comprising a fluid preheater in fluid communication with the fluid conduits within the flame accelerators.
 3. The pressure gain combustion heat generator as recited in claim 2 wherein the fluid preheater further comprises baffles in fluid communication with the combustion chamber.
 4. The pressure gain combustion heat generator as recited in claim 1 further comprising: a. a liner comprising an exhaust portion in fluid communication with the combustion chamber; b. wherein the liner substantially encompasses the combustion chamber.
 5. The pressure gain combustion heat generator as recited in claim 4 further comprising a. a fluid preheater in fluid communication with the fluid conduits within the flame accelerators; and b. wherein the fluid preheater is within the liner.
 6. The pressure gain combustion heat generator as recited in claim 1 wherein the flame accelerators comprise Schelkin spirals.
 7. The pressure gain combustion heat generator as recited in claim 1 comprising a pulse detonation combustor.
 8. The pressure gain combustion heat generator as recited in claim 1, operatively configured to an embodiment wherein fluid entering the fluid inlet is saturated steam and the heated fluid in the outlet is superheated steam.
 9. The pressure gain combustion heat generator as recited in claim 1 wherein the pressure gain combustion heat generator is a detonation based combustor. 